Process and apparatus for cooking wood chips



Feb. 9 1926. l 1,572,723

J. T; JAEGER PROCESS AND APPARATUS FOR CQOKING WOOD CHIPS Feb. 9 1926. 1,572,723

J. T. JAEGER PROCESS AND APPARATUS FOR COOKING WOOD CHIPS 5)/ ATTORNEY y Patented Feb. 9, 1926.

Unirse stares JULIUS THEODORE JAEGER, 0E? RQUGSEALLS, ONTARIO, CANADA.

PROCESS AND APARATUS FR Application tiled April l,

To ZZ whom 'it muy Gericom:

Be it known that l, lomos 'lrnionomi Jimena, a citizen ot the United States of America, and `resident of lroquois Falls, Province of Ontario, Domiuionof Canada, have invented certain new and useful lmproi'ements in Processes and Apparatus for Cooking 1Wood Chips, and do hereby declare the following to be a full, clear, and exact description thereof.

This invention relates to that step in the manufacture of paper wherein Wood chips are enclosed in a vessel termed a digester and there exposed to an acid solution and steam whereby the chips are softened and boiled until reduced to a pulpy mass, this digesting or cookingot the chips being continued for a suitable period to effect a saturation of the wood With the acid and 'sottoning of: the libre preparatory to an ejection of the pulp from the digester for further treatment such as draininq', Washing and screening, in the paper making process.

Heretofore, in the acid treatment outlined above, the contact of the acid solution yand chips Was effected by loading the digester with the chips and solution and satura-ting; and cooking the chips by the admission ot steam,` the agitation of the chips to ensure their treatment and `saturation being dependent upon the ebullition resulting` Within the digester. This prior method presents the disadvantage, with others, that a considerably large charge of acid solution is required in proportion tothe quantity of Wood chips to ensurethe chips being,- completely immersed, and consequently requires a correspondingly lar`V greater amount of solution requires a greater amount of steam and longer application of the latter to bring it to the boilingrpoint. Furthermore in the process heretofore practised the. acid solution is confined Within the digester and consequently the action thereon by the steam in heating the solution to the boiling` point to agitate the mass and pri,6 mote the thorough saturation of the charge of Wood chips in the requisite manner is only secured through the slow process of heating a stationary body of liquid.v is this disadvantage has, in the past, been accentun ated by admitting the steam at one end only of the dige-ster, it Will be apparent that the digesting period has been needlessly protracted, beinggdependent upon the progres-4 sion of the heating throughout the charge o'e amount of `steam as the s COOKNG VOOD CHIPS.

1922'. Serial N0. 548,853.

trom one end of the-digester to the other and subject to the serious defect of uneven treatment owing to the variance of heat at points adjacent to the steam inlet and at remote points near the opposite end ofthe digester.

The primary object ot my invention is to improve existing paper pulp digestingl processes and avoid the above mentioned disadvantages by the establishment ot a circulation of the acid solution, exposed.- to the heating element, through the digester and Wood chip charge and admissionof the heating element to the digester at diiferentl points whereby the acid solution is circulated through the ivood chips thus requiring a smaller charge of solution in proportion to the quantity of chips, to effect the requisite saturation ofI the latterr and calling' for a correspondingly reduced amount of steam for heating, while speeding up the latter action owing to the smaller body of liquidand circulation past the heating element. rlhe admission of the steam at di'lierent points further reduces the heating` period` and establishes a more uniformtreatment or' the charge due to the better distribution of the heating source throughout themass, the different steam charges heating distinct pon tions of the digester content in a uniform manner and thus cooperating to heat they mass as a Whole in a quicker and more even i way.

Another object `is to provide an apparatus for carrying out my improved process.

rlhe above and further objects andl advantageous features of my `invention will he` hereinafter more `fully described in theffollowingdetail specilication and particularly pointed out in the appended claims.`

ln my improved process a vdigester 4is loadedeivith Wood chips and acid admitted with steam to heat the contents andloring them to the boiling point for an effective softening and saturation of the chips. The acid such as sulpliurous acid is admitted at or adjacent the top of the digester to percolate down through the chips thus exposing the whole body of chips to the acid without necessitating,l the use of such a quantity as would 4be necessary to completely immerse the chips, the small quantity of acid in comparison to the quantity of chips enabling the former to be quickly heated by the use 0f a correspondingly reduced quantity of steam. The digester is preferably partially filled with the acid solution from the bottom and through the medium of an injector, steam is utilized to draw this acid from the bottom of the digester and convey it to the top, the acid and steam being discharged upon the chips and passed through the latter trom the top. The acid, preheated by its conveying steam, percolates down through the chips and is again carried to the top, this circulation quickly exposing it tothe steam to rapidly raise its temperature and the passage of the acid through and through the body oit chips, in conjunction with the application of steam to both ends of the digester contents accelerating the attainment of a boiling temperature within the digester and elfecting a thorough and uniform treatment` of the contents.

For full comprehension, however, of my invention reference should be had to the accompanying drawings forming a part of this specification, in which like reference characters indicate the saine parts and wherein F ig. 1 is a front elevation, of a paper pulp digester constructed in accordance with my in vention Fig. 2 is a vei'tical section on line 2-2 Fig. 1; and

Fig. 3 is an enlarged detail section ot the main coupling elbow. n

Referring now to the drawings, 2 indicates the digester proper consisting preterably of a cylindrical steel vessel suitably supported at 3 in upright position and having a top opening 4 and bottom opening 5, the top opening being adapted to be closed by a removable cover 6 and the bottom opening having the several pipes of the apparatus coupled thereto asl will be now described.

A live-way elbow 7 coupled to the bottom opening has a steam supply pipe 8 with valve 3FL leading to the bottom thereof through opening 9 and a. branch steam pipe 10 with valve 10a leading to the elbow from pipe 8 in front of valve 8fL through side opening 11 opposite to a side opening12 to which a conduit 13 leading to the blow pits (not shown) controlled by valve 14 located adjacent, to the elbow.

An acid supply pipe 15 controlled by valve 16 communicates with the elbow through a side opening 17, an oppositely located side opening 18 of the elbow being covered by a grating 19 and connected to one side of an injector 20 by an acid pipe 21 controlled by a valve 22. The injector 20 preferably comprises a casing having a nozzle 23 at the bottom, open to the interior of the casing and directed into a combining tube 24 communicating with the 1nterior of the' casing and leading out through `the top of the latter., .the nozzle being con steam valves 8'L1 is connected, this conduit being nected to an auxiliary steam pipe 25 leading from the steam pipe 8 at a point beyond valve 8 and controlled by valve 26 adjacent the injector. A pipe 27 leads from the coinbining tube 24 to the top of the injector, passing through an opening in cover 6 and through top opening 4 where it terminates in a nozzle disposed at the top ot' the interior of the digester. rNozzle 28 preferably consists of a pipe length 29 flared at its lower end at 30 and having a curved perforated head 3l attached thereto. As shown the head 31 is attached through theinedium oi rbolts 32 carrying washers or distance pieces 33 spacing the head from he flared end of pipe 29 thus providing the nozzle with side openings in addition to the central or front openings constituted by the perforations of the plate.

Acid pipe 21 and auxiliary steam pipe 25 are connected by pipe 34 at a point between'the elbow 7 and the valves 22 and 26 to provide a steam supply to elbow 7 through side opening 18 for a purpose to be presently explained, this pipe 34 being controlled by valve 35.

My process is cariied out with the above described apparatus as follows:

lith opening 4 cleared of cover 6 and nozzle and with valves 8, 10, 14, 22, 26 and 35 closed, the digestcr is loaded with a lull charge of wood chips and the acid solution admitted by opening valve 16, the solution passing through openings 17 and up through bottom opening 5 into the d igester, a portion of the acid, assisted by the static pressure within the digestei, entering the injector through pipe 21. The acid is admitted only in sulicient quantity to par-- tially lill the vessel, that is to about the y level as indicated particularly in Fig. 2. At this Vtime valve 16 is closed and opening 4 also closed by the insertion of the acid nozzle and cover 6, the latter being fastened in av suitable manner and thc digester interior with its pipe system thus sealed from the atmosphere.

The above preparation being'con'ipleted and 26 and acid valve 22 are opened to direct steam through opening 9 of the main coupling elbow nd bottoni opening' 5 of the digester into vthe interior of the latter and through pipe 25 into the injector. The steam admitted at the bottoni of the digester comes into cont ct with the acid and wood chips and inaugurates the heating action which progresses upwardly through the ldigester contents and at the same time a similar heating action is inaugurated at the top of the digester as follows. Steam blo-wing from the pipe passes through the injector, creating a vacuum therein and drawing acid with it up through pipe 27 to tl the injector., the acid and steam being ie nozzle at the top ci.

ll l) sprayed Yfrom the nozzlevover the'top of the chips. he. tront and lateral openings o't the nozzle distribute the discharge completely and unilormly over the top ot the Wood chips thus evenly enveloping the latter and causing the acid to percolate doivn through the chips throughout the itull cross-sectional area ol the charge, the spraying ot the hot acid over the top ot the chips protecting them from dry heat and avoiding the possibility oit deterioration dus to charring. ln being conveyed from the injector to the top ot the digester the acid is exposed to the steam and thereliiy preheated before being discharged upon the chips, this admission oit preheated acid and the steam at the top ot the digester e'li'ecting a heating action at the top which progresses downwardly through the digester contents. rThe described adniission ot' steam at both ends ot the digester heats the acid Within the digester and inaugurates the boiling process at both top and bottom, the steam supplies at distinct points "within the vessel and acting upon separate portions rot the contents, co-operating to quickly raise the temperature ot the Whole mass.

During theheating oit the acid, condensation ot the steam ensues owing to its contact With the cooler acid andthe vessel becoming filled n'ith a mixture oit acid and condensed steam, circulation oztl the acid Ytroni bottoni to top o't the digester is retarded. To dispose oit the excess liquid a relie't pil is provided, this pipe leading :trom a point near the top ot' the digcster to a cooler and reclainiing tank (not shown) and being controlled by a manually' closed valve 37 which is opened When the digester tills and alloivs the liquid to be draivn ott iti-cin the top oit the digester to re-establish the circulation, at which the valve 37 is closed. lVhen the temperature of the acid solution is equalized with that of the enteru ing steam, condensation ceases and circulation is delinitely established, being inain tained by providing an outlet for gas naturally 'forming at the top oit the digester. This gas outlet comprises a gas reliet pipe 38 leading from the top of the digester and controlled by va valve 39 Whichis kept shut excepting at such times as it is opened as required to relieve gas which accumulates at top ot digester with circulation.

ln the circulation above explained, the acid content ott the vessel is carried trom the bottoni et the digester to the top and thus passed through and through the body ot chigs and into contact with the entering steam, thereby accelerating the heating of the acid and quickly bringing it to the boiling point, the boiling acid penetating the chips and softening the Wood libre.

lleretofore as above mentioned, the digesting vessel has been `lilled with acid `to near the topv and the acid maintained Within the vessel without circulatiomsteam being -ad inittedv at one end, the heating action pro-` gressing trom one end to the other et the stationary body or liquid. ln comparison with this relatively sloiv attainment ot boiling temperature progressively from one end ot the digesting vessel to the other, the present process ot inangurating the boiling at both ends o't the digester and pcrcolating the acid through the chips enables a lesser quantity et acid and correspondingly reduced quantity ot' steam Ylor heating it to be used and more rapidly establishes the boiling tein- 'erature throughout the vessel dueto the distribution ot the heat sources at distinctly spaced points ot the body ot chips and the circulation established by the percolation method :to carry the heated acid quickly throughoutall parts ot the body ot chips. The acid circulation turtherinore ettects a breaking up action upon the body of chips to agitato the mass so that troni the commencement ot the digesting process am prior to the boiling period all the chips are intimately exposed to the heat to the end that a heating and subsequent boiling tenipcrat-ure is rapidly secured and a thorough acid reaction eiiected resulting ina desirable high degree of uniformity yof product.

The. boiling process is carried on t'or a ,suitable period, i. e., seven to eight hours, the valve 16 being then closed and tbc pulp blown from the digestcr to the pits, by opening valves l0 and let, the above boiling period being oit considerably reduced duration With respect lo prior processes as the boilingwith rapid circulation and percolation ot heated acid over the chips is substantially uni'torm over the Whole vessel and raises the temperature and cllects the treatment ot the chips `laster than heretofore.

The action ol1 injector 20 in drawing the acid trom the bottom ot the digester through elbow 7 and opening 1S to the pipe '2l naturally tends to carry certain of the chips with the acid, such chips being obstructed by the grating 19 from entering the pipe and in order to avoid the blocking of this passage by the clogging of the grating the branch steam pipe 34 is provided, valve 85 being periodically opened to blow steam inwardly through the grat-ing and dislodge the accumulated chips.

1*filhat l claim is as `t'ollows:

l. An apparatus for the treatnientV ot Wood chips in the production o't pulp, in cluding in combination, a vessel 'lor containing th-e chips, a'steain supply pipe communicating with the vessel adjacent one end thereoiand acid supply Yfor the vessel, an acid conveying pipe leading 'from one end ol the vessel to the opposite end thereof into which it discharges and ineens tor circulating the acid from one end of the vessel, through said acid pipe, into the opposite end or' the vessel and anozzle upon the discharge end of the acid circulation pipe, such nozzle coi'nprising a pipe length presenting a flared front end, a perforated head covering the flared end and means forsecuring the head in spaced relation with respect to the flared end ot the pipe length to present side openings additional to the perforations of the head.

2. An apparatus 'for the treatment of wood chips in the production of pulp, including in combination, a vessel for containing` the chips, aste-ani supply pipe comn'uinicating with the vessel adjacent one end thereo'i and n'ieans for circulating` the acid out from one end oi the vessel into the opposite end, such meansineluding a steam pipe discharging into such opposite end of the vessel, an injector in the steam pipe, an acid conveying pipe leading from the vessel into the injector and a grating extending over the acid pipe at a. point adjacent the vessel., to exclude chips from said pipe.

3. An apparatus vfor the treatment ol wood chips in the production oil pulp, in cluding in combination, a vessel for containing the chips, a steam supply pipe communicating with the vessel adjacent one end thereof and means .tor circulatingl the acid out from one end of the vessel into the opposite end, such means including a steam pipe discharging into such opposite end of the vessel, an injector in the steam pipe, an acid conveying pipe leading from the vessel into the injector, a grating extending over the acid pipe at a point adjacent the vessel,

to exclude chips from said pipe, and a steam supply pipe leading into the acid pipe at a point between the grating and injeetor whereby steam can be blown through said grating towards the vessel to clear the grating` of adhering chips.

ll. An apparatus :tor the treatment of vwood chips in the production of pulp including, in combination, a vertically disposed elongated vessel having top and bottom openings, a cover tor sealing the top of the vessel, an elbow closing the bottom opening, a valve closed acid supply pipe leading into the elbow, a valve controlled main steam supply pipe leading into the bottom of the elbow, a valve controlled auxiliary team pipe leading from the main steam pipe exteriorly et `the vessel, through the top cover Koi the vessel and discharging into the top or" the latter, a spraying nozzle upon the discharge end of the auxiliary steam pipe, aninjector in the auxiliary steam pipe, a valve controlled acid conveying pipe leading from the elbow into the injector, a grating extending over the acid conveying pipe at a point adjacent. the elbow, a valve controlled pipe connecting the auxiliary steam pipe and acid conveying pipe at a point between the valves of said pipes and the elbow, a valve controlled branch steam pipe leading from the main team pipe into the elbow at the side thereo-:t and a valve controlled pulp discharge conduit leading; from the elbow at the opposite siee to the branch steam-pipe.

ln testimony whereof, I have signed my name to this specification.

JULlUS THEODOPE JAEGER. 

